University of Kansas Publications Museum of Natural History Vol. 18, No. 4, pp. 253-420, 26 figs., 7 pis. July 7, 1969 Natural History of the Hognose Snakes Heterodon platyrhinos and Heterodon nasicus BY DWIGHT R. PLATT University of Kansas Lawrence 1969 University of Kansas Publications, Museum of Natural History Editors of this number: Frank B. Cross, Philip S. Humphrey, J. Knox Jones, Jr. Volume 18, No. 4, pp. 253-420, 26 figs., 7 pis. Published July 7, 1969 University of Kansas Lawrence, Kansas PRINTED BY ROBERT R. (BOB) SANDERS, STATE PRINTER TOPEKA, KANSAS 1969 32-4332 Natural History of the Hognose Snakes Heterodon platyrhinos and Heterodon nasicus BY DWIGHT R. PLATT CONTENTS PAGE Introduction 256 Acknowledgments 258 Methods 259 Description of Study Areas 261 Morphology 265 Taxonomic Status 281 Fossil Record and Evolutionary History 285 Geographic Range and Habitat 287 Temperature 299 Periodicity 305 Shelters and Burrowing 316 Locomotion and Prowling Behavior 320 Home Range and Movements 321 Reproduction 325 Growth and Ecdysis 347 Food Habits 361 Disease and Mortality 375 Population 385 Relation to Man 393 Ecological Comparisons 394 Summary 398 Literature Cited 405 (255) 256 University of Kansas Publs., Mus. Nat. Hist, INTRODUCTION Because of their peculiar morphology and interesting behavior, hognose snakes, genus Heterodon, have been extensively featured in popular literature. Even so, little is known about many aspects of their ecology and most of what is known is to be found in scat- tered notes. Some of the more important contributions to our of snakes are those of Surface 1906 Uhler knowledge hognose ( ) , et al (1939), Clark (1949), and Hamilton and Pollack (1956) on the food of the eastern of 1892a Clark hognose snake; Hay ( ) , (1952a, 1952b), and Kennedy (1961) on reproduction of that spe- cies; of Munro (1949b, 1949c) on reproduction of a western hog- nose snake; of Davis (1946) on burrowing of the eastern hognose; of 1961 varia- Edgren ( 1952a, 1952b; 1955; 1957; ) on geographical tion, taxonomy, evolution, and natural history of hognose snakes; and of 1965 their Weaver ( ) on cranial anatomy. There are three species in the genus Heterodon. The eastern hognose snake (Heterodon platyrhinos) is found over much of eastern North America and west through parts of the prairie. The range of the western hognose snake (H. nasicus) is in the Great Plains from Mexico into southern Canada. The southern hognose snake [H. simus), not included in this report, is restricted to the southeastern coastal regions of the United States from southern North Carolina to south-central Florida. There is no evidence of hybridization between the eastern hognose and the western hog- nose in their area of sympatry. Although hognose snakes are not abundant over much of their range, they are known to farmers and other persons who spend much time outdoors. The peculiar defensive "bluflBng" behavior of the eastern hognose, involving hissing, expanding the neck, and mock strikes, is notorious. This behavior and the broad triangular head have given rise to many stories concerning the venomous nature of hognose snakes. In certain localities the eastern hognose is sometimes mistaken for the copperhead (Agkistrodon contortrix) , or thought to be closely related to this venomous species. (See p. 366; Hay, 1892a: 116; Morse, 1904:127; Ditmars, 1905:104; Netting, 1927:30-31; Myers, 1929:101; Welter and Carr, 1939:129; Brimley, 1941:23; Wheeler, 1947:165.) Although such fallacious ideas per- sist, I found that many lay persons who have had experience with hognose snakes recognize that they are harmless. More than 50 common names have been given to the eastern hognose, the ma- Natural History of Hognose Snakes 257 jority reflecting a belief in its venomous nature (Schneck, 1878:586; Strecker, 1928:14; McCauley, 1945:63; Wright and Wright, 1957: 306 ) . More than 20 common names have been used for the western hognose (Wright and Wright, 1957:297, 302). of were : 1 to The objectives my study ( ) determine the ecological niches occupied by sympatric populations of eastern and western hognose snakes in two natural communities in south-central Kansas; (2) to compare the adaptations, ecology, population dynamics, and life history of the two species, and to attempt to determine the biological significance of differences and similarities; (3) to deter- mine factors limiting the geographic distributions of the two spe- cies; (4) to determine the nature and degree of morphological variability of hognose snakes. Because of their burrowing habits and their lack of aggregation behavior during hibernation, hognose snakes usually cannot be collected in large numbers. The present report is based primarily upon records obtained by live-trapping snakes on two study areas, Harvey County Park and Graber Pasture, in the sand prairies of south-central Kansas, from May 6, 1959, to November 18, 1963. In five seasons 241 western hognose snakes were captured 314 times on the two study areas. A total of 124 eastern hognose snakes were captured 144 times. Live-trapping on the study areas was supple- mented by collecting in the surrounding sand prairie area. It was not possible to make intensive studies of other popula- tions of hognose snakes in the center of the allopatric portions of the range of each species. However, the study in central Kansas was supplemented by visits to other localities where hognose snakes have been found in Kansas, southeastern Missouri, Illinois, Iowa, and North Carolina. Also, information was obtained from the literature and from persons familiar with these snakes in other parts of their ranges. 258 University of Kansas Publs., Mus. Nat. Hist. ACKNOWLEDGMENTS Many persons and organizations have aided in this study. Dr. Henry S. Fitch has been especially helpful. He gave me the opportunity to work as an assistant in his research on the ecology of snakes ana has given many helpful suggestions at all stages of the project. Special thanks are also due to the following persons: Dr. A. Byron Leonard and Mr. James W. Bee for advice on histological technique and photography; Dr. William E. Duellman for helpful counsel, editorial suggestions, and use of his personal library; Dr. Lloyd C. Hulbert for helpful suggestions and data concerning the plant communities on the study areas; and Dr. Edward Batschelet, Mr. G. M. Jolly, and Dr. Arnold M. Wedel for suggestions concerning statistical methods. Without the help of these persons, the study would have been much less adequate. However, any errors or misinterpretations are the responsibility of the author. Mr. Roy W. Henry, Dr. W. Dale Horst, and Mr. Howard L. Schrag assisted with the field work in Harvey County, Kansas. Identifications of parasites were made by Dr. S. L. Loewen (trematodes) and Mr. W. W. Becklund (nematodes). Dr. John L. Buckley and Mr. William H. Stickel of the U. S. Fish and Wildlife Service Patuxent Wildlife Research Center made available the data in their files concerning the food of and predation on hognose snakes. Mr. Charles H. Rousell, Mr. Robert C. Waltner, Mr. Harvey Holzrichter, and the late Mr. Ralph Woods collected specimens for me in south-central Kansas. Mr. Tom Swearingen advised and assisted in the preparation of graphs and maps. The following persons have supplied information on or specimens of hognose snakes from other parts of the ranges of the eastern and western species: the late Mr. Paul Anderson, Dr. Richard J. Baldauf, Dr. Monroe H. Bartel, Dr. W. J. Breckenridge, Dr. Bryce C. Brown, Dr. Kenneth D. Carlander, Mr. Roger Conant, Mr. Francis R. Cook, Dr. Donald G. Dunlap, Dr. Carlos S. Folger, Dr. John W. Forsyth, Dr. Carl Cans, Dr. Claude W. Hibbard, Mr. H. T. Hiemstra, Mr. W. Charles Kerfoot, Mr. E. B. S. Logier, Mr. Robert J. Mangile, Dr. T. Paul Mashn, Mr. Herbert Milnes, Dr. Sherman A. Minton, Jr., Dr. Gerald G. Raun, Dr. Philip W. Smith, Mr. Ernest C. Tanzer, Dr. Donald W. Tinkle, Mr. L L. Traill, Dr. Robert G. Webb, and Dr. George C. Wheeler. I am grateful to curators of herpetological collections in the following insti- tutions who either provided information concerning specimens or allowed me to examine specimens: Chicago Academy of Sciences, Field Museum of Natural History, Fort Hays Kansas State College, Kansas State Teachers Col- lege at Emporia, Kansas State University, Stanford University Natural History Museum, Texas Cooperative Wildlife Museum, United States National Museum, University of Kansas Museum of Natural History, and University of Michigan Museum of Zoology. I thank Mr. Harry Graber and Mr. John Randall for permission to trap snakes and pursue other studies on their properties. Mr. George Hawkes, caretaker, kindly allowed me to establish a study area in Harvey County Park. I am particularly grateful to the National Science Foundation for giving financial assistance to my study. Much of the field work from 1959 to 1962 was financed by National Science Foundation grants G-6158 and G-16104 to Dr. Henry S. Fitch of The University of Kansas Department of Zoology. I was employed as research assistant on the project supported by these funds in 1959 and 1960. From 1960 to 1962 I was assisted by a National Science Foundation Cooperative Graduate Fellowship. My wife, LaVonne Piatt, has aided me by copying notes, typing, assisting in statistical computations, and editing; and has encouraged me in all phases of the work. Natural History of Hognose Snakes 259 METHODS Natural populations of hognose snakes in Harvey County, Kansas, were studied primarily by live-trapping, marking, releasing, and recapturing. Cylin- drical traps of galvanized wire "hardware cloth" of quarter-inch mesh with funnel entrances were used (Fitch, 1951; 1960b:93-94). Each trap station consisted of a straight drift fence 15 to 20 feet long and 8 to 12 inches high of wood or galvanized "hardware cloth" with a furmel trap fitted on either end.